Our laboratory has a long standing interest in development of immunochemical methods for cell separation, for studying receptor-mediated activation of T cells, and in the role of T cells in tumor rejection. With respect to immune activation, we are particularly interested in developing methods for the direct measurement of biologically important but relatively low affinity immune interactions. Such methods include the use of semisynthetic multivalent macromolecular reagents ("polygens"), and recombinant multimeric protein domains. These constructs, which increase the effective valence of protein epitopes, may help to make it possible to do direct measurements of such interactions as between the T cell receptor and peptide-pulsed MHC antigens. During this year, I have been doing an intramural sabbatical in the laboratory of Dr. David Margulies, LI, NIAID, in order to expand my capabilities by obtaining experience and training in molecular biology, in the context of Class I MHC molecules. In my sabbatical work, I have prepared a biologically active recombinant single chain Class I MHC molecule, potentially useful for structural studies, and for studying interactions of MHC molecules with antigenic peptides and T cell receptors.